1. Field of the Invention
The present invention relates to a bar code reader which is capable of precisely scanning the bar code information by a modulated laser beam.
2. Description of the Prior Art
Conventional bar code reader is illustrated in FIG. 1, which is structured with reflective mirrors 4 and 4' for reflecting a laser beam generated from a laser beam generator 3 toward a hologram disk 1, a mirror member 5 for forming a scanning pattern by reflecting a laser beam at various angles which is diffracted and scanned by the hologram disk 1, a photodetector 8 for detecting the beam focused on a focusing lens 7 after being reflected from the reflective mirror 4', and a signal analyzing unit 9 for analyzing and processing the output signal of the photodetector 8.
The laser beam generated from the laser beam generator 3 according to such conventional bar code is reflected from the reflective mirror 4 and the laser beam thus reflected passes through the focusing lens 7, thereafter reflected from the reflective mirror 4' and entered into the hologram disk 1. The hologram disk 1 is structured by a number of holograms 1a disposed radially on a circular plate in a predetermined angle as shown in FIG. 2.
Accordingly, as the hologram disk 1 rotates upon the driving of the motor 2, the laser beam being incident upon the hologram disk 1 is diffracted by the hologram disk 1 and scanned on the mirror member 5, thereby a scanning pattern is formed by the mirror member 5 and is scanned through a window 6 on an object 12 that a bar code is printed. At this moment, the laser beam is dispersed by the bar code printed on the object 12 and the dispersed laser beam is focused on the focusing lens 7 after passing through the window 6, the mirror member 5 and the hologram disk 1, then the focused laser beam is detected by the photodetector 8 and analyzed and processed by the signal analyzing unit 9, thereby reading the bar code information of the object 12.
However, such conventional bar code reader have a number of problems such as, for example, since the sizes of the mirror member for forming the scanning pattern, the holograms for constituting the hologram disk, the reflective mirrors and focusing lens have to be large in order to increase the quantity of the beam detected at the photodetector, thereby giving rise to the increase in size and cost of the system.